1. Field of the Invention
This application relates to mounting mechanisms for surge suppressors used for an antenna system in telecommunication facilities.
2. Description of the Related Art
For cellular equipment towers, antenna cables which are exposed to lightning need to be properly grounded and bonded to the building grounding system to prevent damage to equipment, property and injury to personnel from the lightning.
For antenna cables, a standard approach provides exterior conductor grounding (outer sheath) to the roof ground ring or tower ground system prior to the cables turn toward the building entrance. About 10 percent of the voltage carried by the outer sheath or conductor can be induced on the center conductor, even though the center conductor is insulated from the outer sheath. That induced voltage is not clamped to ground via the rooftop cable grounding kit (which is only designed to protect the outer conductor), and can enter the building and equipment unimpeded and create dangerous arcing to other ground sources with different potentials. A surge suppressor is designed to shunt the foreign voltage on the center conductor to a ground source that is referenced to the building's ground system as soon as is practicable upon entering the building. Numerous models of surge suppressors, such as from Polyphaser™ Corporation, provide voltage protection to equipment property and personnel from foreign voltage, which can be induced on the center conductor of the coaxial cable during a lightning strike.
Traditional equipment locations in some communications facilities may provide a higher level of electrical and grounding protection than typically encountered at other building equipment locations such as Collocation Hotels, and privately owned high-rise buildings where communication companies may lease rooftop and building spaces.
Prior approaches for mounting or installing such surge suppressors for antenna cabling have used common electrical cabinets for all users of the facilities of insufficient gauge or ground reference. Such installation typically utilizes ad hoc field drilling or Greenlee Punching, which subjects all previous installations to risk when adding additional surge suppressors. The traditional electrical cabinets are painted, 12 gauge steel and do not provide the surface area, conductive material or minimum material thickness required to provide a reliable grounded surge suppressor mounting surface. In addition, the traditional electrical cabinets are often only bonded to the building ground system using a #6AWG conductor. In locations where multiple cellular providers share a tower, one company's surge suppression equipment may interfere with another company's equipment and installation of additional surge suppressors may in fact pose a risk to service during the installation due to damage to cabling. Improper or inconsistent grounding of each antenna cable and surge suppressor may create differences in potential at the cabinet, which could result in arcing and current flow to those cables with less resistance or fewer ohms to ground. Thus, current approaches to installation of surge suppressors for antenna cabling at cellular towers are inadequate for a number of reasons.